Radio telescope mounted within lighterthan-air gas filled balloon to lessen support stress



March 29, 1966 w. PLEASANTS 3,243,817 RADIO TELESCOPE MOUNTED WITHIN LIGHTER-THAN-AIR GAS FILLED BALLOON TO LESSEN SUPPORT STRESS 2 Sheets-Sheet 1 Filed Feb. 11., 1964 AXIS INVENTOR. M7115; BZP/mzzfis,

4170mm ysi arch 29, 1966 w. w. PLEASANTS 3,243,817

RADIO TELESCOPE MOUNTED WITHIN LIGHTER-THAN-AIR GAS FILLED BALLOON TO LESSEN SUPPORT STRESS Filed Feb. 11, 1964 2 Sheets-Sheet 2 INVENTOR.

4 TIDE/KEYS.

United States Patent 3,243,817 RADIO TELESCOPE MQUNTED WITHIN LIGHTER. THAN-AIR GAS FILLED BALLOON T0 LESSEN SUPPORT STRESS William W. Pleasants, R0. Box 6, Green Bank, W. Va. Filed Feb. 11, 1964, Ser. No. 344,093 9 Claims. (Cl. 343-765) This invention relates generally to radio telescopes and particularly to improvements in reflectors and reflector supports for such telescopes.

In the design of reflectors and reflector supports for radio telescopes, the desideratum is an arrangement whereby the various factors which cause distortion of the structure are held to a minimum. Many ways of achieving the desired end have been suggested, but these have not proved to be entirely satisfactory when considered in the light of cost, weight, maintenance and predictable useful life.

Polar mounted reflectors, especially in the larger sizes, are particularly sensitive to various factors which cause distortion. For example, if the reflector is not protected against the elements, the structure must withstand live loads, i.e., loads due to wind, snow, ice, etc. In this event, the size of the reflector is sharply limited because deflection of the reflecting surface must be kept within prescribed limits in order to achieve the desired degree of accuracy.

Even when the reflector is protected against the elements, the size of the reflector is sharply limited by its dead weight, which must be kept within prescribed limits to facilitate orienting the reflector about the polar and declination axes.

Accordingly, a principal object of the invention is to provide a radio telescope having a polar mounted reflector effectively protected from the elements to minimize the load thereon and so arranged that only a portion of its dead weight need be supported by the polar mount.

Another object is to provide such a telescope wherein, without sacrificing accuracy, for a given dead weight the reflector may be larger in diameter or for a given diameter the dead weight of the reflector may be reduced.

Another object is to provide such a telescope with a helium inflated radome arranged to reduce the dead load on the declination shaft whereby to facilitate movement of the reflector about the polar and declination axes.

Other objects of the invention will become apparent when the following description is read with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation of a radio telescope having a polar mounted reflector and radome constructed in accordance with the invention;

FIG. 2 is a view indicated by line IIII in FIG. 1;

FIG. 3 is a view indicated by line IIIIII in FIG. 1;

FIG. 4 is an enlarged section on line IVIV in FIG. 1;

FIG. 5 is a reduced section on line VV in FIG. 4;

FIG. 6 is an enlarged section on line VI-VI in FIG. 5;

FIG. 7 is an enlarged section on line VII-VII in FIG. 3; and

FIG. 8 is an enlarged section on line VIIIVIII in FIG. 3.

The following description is directed to the specific embodiment of the invention illustrated in the drawings and is not intended to be addressed to the scope of the invention itself, which may be practiced in a variety of forms.

The exemplary radio telescope constructed in accordance with the invention is mounted upon the ground, the surface of which is designated 10. A concrete footing 12 carries a bearing 14 which mounts a polar yoke, generally designated 16, provided with a shaft 18 received by the bearing 14. The axis of the shaft 18 is coincident with the 3,243,817 Patented Mar. 29, 1966 polar axis, designated 19. The yoke is provided with a cross member 20 from opposite end portions of which extend two laterally spaced arms 22 and 24. A position indicator 2-5 is associated with the shaft 18.

Two other concrete footings 26 each carry a pair of bearings 28 which respectively receive the opposite end portions of a shaft 30. The shaft 30 carries a roller 32. Mounted upon the companion rollers 32 is a semicircular open frame structure or cradle, generally designated 34. The cradle is provided with an inner cord 36 comprising laterally spaced channel members 38 and cross ties 40, and with an outer cord 42 comprising flange plates 44 and 46. The inner cord 36 and the outer cord 42 are tied together by means of web members 48 each secured to the top cord 36 by means of a gusset plate 50 and to the bottom cord 42 by means of a gusset plate 52. Aflixed to the flange plate 44 are two laterally spaced shoe plates 54 mounting therebetween an arcuate rack 56. Aflixed to opposite sides of each footing 26 are a pair of plates 58 respectively mounting a pair of rollers 66 overlying the flange plate 44.

The outer extremities of the arms 22 and 24 of the yoke 16 are provided respectively with branches 62 and 64 by means of which they are suitably secured respectively to the extremities of the cradle. Extending through the branch 62 and the inner cord 36 is a short pivot shaft 67, and extending through the branch 64 and the inner cord 36 is a short pivot shaft 68. The axes of the shafts 67 and 68 are coincident with the declination axis, designated 69. Carried by the arm22 is a base 70 mounting a motor and reducer unit 72. The output shaft of the unit mounts a pinion '74 meshing with a gear 76 mounted upon the shaft 67. Mounted upon the branch 64 of the arm 24 is a bearing 78 which receives the shaft 68, and associated with the shaft 68 is a position indicator 80.

The shafts 67 and 68 mount an open frame structure 84 which carries a dished reflector surface 86. Converging upwardly from the reflector are a set of four feed supports 88 at the apex of which is mounted a feed 90.

Referring particularly to FIG. 4, the inner end of the shaft 67 is affixed to a plate 92. Circumferentially spaced about the shaft 67 are a plurality of members 94 the inner ends of which are affixed to plate 92 and the outer ends of which carry an annular ring 96. The ring 96 is provided with a pair of legs 98 and 100, the leg 98 being secured to the members 94 by means of bolts 102. Another ring 96 is associated in like manner with the shaft 68.

The feed 90, feed supports 88, reflector 86 and frame structure 84 are enveloped in a balloon, generally designated 104. The upper half of the balloon, designated 105, is secured to the lower half of the balloon, designated 107, by overlapping the marginal areas thereof and clamping them together by means of an outer band 109 secured by means of screws 113 to a suitable inner band 111. The edges of the fabric are rolled, as at 115 and 117.

Each of the shafts 67 and 68 extends through an opening in the balloon fabric on the associated side of the balloon. The marginal fabric area defining each opening overlies the leg of the associated ring 96. Each opening is closed by a panel of balloon fabric 119 which overlaps the marginal fabric area defining the opening. The overlapping marginal fabric areas are clamped to the leg of the ring 96 by means of annulus 112 secured by means of screws 116. The edges of the marginal fabric area defining the opening are rolled, as at 114, and the edges of the panel 110 are rolled, as at 118. Each shaft 67 and 68 extends through the associated panel 110, as at 119, being rolled, as at 122, and is secured to the shaft by means of a clamp 120.

A pinion 124 meshes with the rack 56 and is mounted upon the output shaft 126 of a motor and reducer unit generally designated 128, seated upon a base 132.

In the use of the apparatus, the balloon 104 is filled with helium. The unit 128 is operated to position the reflector 86 about the polar axis 19. The unit 128 operates to actuate pinion 124, and the pinion 124 actuates the arcuate rack 56, which turns the cradle 34 about the polar axis 19. The cradle 34 rests on and is guided by rollers 32 underlying plates 54 and is held down and guided by rollers 66 overlying plate 44. Since the cradle 34 and the polar yoke 16 are rigidly interconnected at their extremities, the cradle turns the polar yoke about the polar axis 19, i.e., about the axis of shaft 18. The declination axis 69 is thereby tilted, and the frame structure 84 and reflector 86 are oriented about the polar axis 19.

Motor and reducer unit 72 is operated to position the reflector 86 about the declination axis 69. The unit 72 operates through pinion 74 and gear 76 to turn shaft 67, frame structure 84, shaft 68 and the reflector 86. Thus the reflector 86 is oriented about the declination axis 69.

It has been proved by suitable tests that the wind loads on a structure are held to a minimum when the structure is spherical in shape. Thus, preferably, a spherical balloon is used. In practice, the helium filled balloon may be suitably lashed to the ground at two or more points.

If snow accumulates upon the balloon 104, the balloon may be turned about either or both axes, or the internal pressure may be varied to dislodge the snow. The balloon 104 may be of a diameter only slightly larger than the diameter of the reflector 86, reflector diameters in the order of 125 feet being contemplated. It is to be noted that the reflector and the balloon move together.

The helium filled balloon 104 protects the reflector 86 from the elements, in consequence of which the reflector may be designed to sustain only the dead weight of the reflector. Thus the reflector may be made larger in diameter for a given dead weight or lighter in weight for a given diameter, without sacrificing accuracy. Since tests show that a spherical shape is best for minimizing wind loads, the spherical balloon reduces the live load on the polar yoke 16 and cradle 34, which is desirable because by reducing the load on the shafts 67 and 68, it becomes comparatively easy to turn the structure about the polar and the declination axes.

What is claimed is:

1. In a radio telescope, the combination comprising means providing a dished reflecting surface, a rigid structure including coaxially related pivots extending outwardly in opposite directions from said rigid structure, a balloon filled with lighter than air gas enveloping said refleeting surface and rigid structure and having said pivots extending through diametrically opposite sides thereof, means securing said balloon to said rigid structures for applying thereto its lifting effort, ground supported means providing journals for said pivots and mounted for turning about an axis intersecting and normal to the axis of said pivots, means for turning said reflector surface, rigid structure and balloon as a unit on said pivots, and means for turning said reflector surface, rigid structure, balloon and ground supported means as a unit about said axis intersecting and normal to the axes of said pivots.

2. The combination defined in claim 1 wherein the balloon is spherical and filled with helium.

3. The combination defined in claim 1 wherein the balloon is secured to the pivots.

4. The combination defined in claim 1 wherein the balloon is spherical and only slightly larger in diameter than the reflecting surface and rigid structure.

5. The combination defined in claim 1 wherein the ground supported means comprises a yoke and a cradle each embracing the balloon and disposed in downwardly diverging relation with the extremities of the yoke connected respectively with those of the cradle to provide journals for receiving the pivots.

6. The combination defined in claim 5 wherein the yoke is mounted for pivotal movement about its principal longitudinally extending axis, and the cradle is arcuate in shape and operable for turning said yoke about said principal longitudinally extending axis.

7. The combination defined in claim 6 wherein the yoke and cradle are disposed normal to each other.

8. The combination defined in claim 6 wherein the cradle is mounted upon stationary roller means at its outer periphery and actuated by a positionally fixed pinion meshing with an arcuate rack extending about its periphery.

9. In a radio telescope, the combination comprising means providing a dished reflecting surface, a rigid structure underlying said reflecting surface including coaxially related pivots extending outwardly in opposite directions from said rigid structure, annular members respectively extending about said pivots and fixed relative to said rigid structure and pivots, a balloon filled with helium enveloping said reflecting surface, rigid structure and annular members and having said pivots extending through diametrically opposite sides thereof, means securing the fabric of said balloon to said annual members for applying the lifting effort of the balloon thereto, ground supported means providing journals for said pivots and mounted for turning about an axis intersecting and normal to the axis of said pivots, means for turning said reflector surface, rigid structure, annular members and balloon as a unit on said pivots, and means for turning said reflector surface, rigid structure, annular members, balloon and ground supported means as a unit about said axis intersecting and normal to the axis of said pivots.

References Cited by the Examiner UNITED STATES PATENTS 2,134,932 11/1938 Smith 33-226 2,212,346 8/1940 Kroon 33-61 2,512,636 6/1950 Flynt 343765 2,530,890 11/1950 Mattke 343-765 3,075,191 1/1963 Peay 343915 3,147,478 9/1964 Bird 343765 OTHER REFERENCES Wright, Palomar: The MacMillan Company, New York, 1962 pages 15 8-159 relied on.

HERMAN KARL SAALBACH, Primary Examiner.

ELI LIBERMAN, Examiner.

R. F. HUNT, Assistant Examiner. 

1. IN A RADIO TELESCOPE, THE COMBINATION COMPRISING MEANS PROVIDING A DISHED REFLECTING SURFACE, A RIGID STRUCTURE INCLUDING COAXIALLY RELATED PIVOTS EXTENDING OUTWARDLY IN OPPOSITE DIRECTIONS FROM SAID RIGID STRUCTURE, A BALLOON FILLED WITH LIGHTER THAN AIR GAS ENVELOPING SAID REFLECTING SURFACE AND RIGID STRUCTURE AND HAVING SAID PIVOTS EXTENDING THROUGH DIAMETRICALLY OPPOSITE SIDES THEREOF, MEANS SECURING SAID BALLOON TO SAID RIGID STRUCTURES FOR APPLYING THERETO ITS LIFTING EFFORT, GROUND SUPPORTED MEANS PROVIDING JOURNALS FOR SAID PIVOTS AND MOUNTED FOR TURNING ABOUT AN AXIS INTERSECTING AND NORMAL TO THE AXIS OF SAID PIVOTS, MEANS FOR TURNING SAID REFLECTOR SURFACE, RIGID STRUCTURE AND BALLOON AS A UNIT ON SAID PIVOTS, AND MEANS FOR TURNING SAID REFLECTOR SURFACE, RIGID STRUCTURE, BALLOON AND GROUND SUPPORTED MEANS AS A UNIT ABOUT SAID AXIS INTERSECTING AND NORMAL TO THE AXES OF SAID PIVOTS. 